Microstructural Evolution during Spheroidization Annealing of Eutectoid Steel: Effect of Interlamellar Spacing and Cold Working

Abstract

Eutectoid steels present a wide range of interesting mechanical properties (high strength, wear resistance, ductility and toughness) and could be a cheaper alternative to high strength low-alloyed steels (HSLA) in applications where weldability is not a critical requirement. The mechanical properties of pearlite are mainly dictated by the interlamellar spacing and the spheroidization of cementite. In this work, the spheroidization kinetics during annealing of a fully pearlitic steel produced in an electric arc furnace (EAF) is investigated. More specifically, the influence of a prior cold deformation and of the interlamellar spacing is studied using image analysis and hardness tests. It is shown that spheroidization is faster in fine pearlite than in coarse pearlite. Prior cold deformation strongly accelerates the spheroidization kinetics in fine and coarse pearlite. The tensile properties corresponding to different pearlite microstructure were measured and are compared to the hardness evolution during annealing.